RedFlow Batteries Split from New Inverter thread

[RossW]

was just looking at the  REDFLOW site and they now have several inverters that will work for their power 'cells',...   

In the last month, I've been in contact with their CEO (who I knew from a previous life in the ISP game), seriously considering going that route.

Wow, what a disappointment.

They're built on 10kWh modules, and when they say they'll always have the full 10kWh capacity, what is less obvious is that you need to put around 12.5kWh into them (new) and up to 14kWh or so, after their rated number of cycles. So cycle efficiency is fairly low.
Also, you cannot just "add more electrolyte and bigger tanks" for longer run time. They don't work like that, they're a hybrid flow cell. Basically, you use power to deposit zinc onto plates to "charge", and then recover that power by returning zinc to the electrolyte. The capacity is therefore more "how much zinc you can fit on the plates".
Next was the relatively low charge and discharge rates. A maximum sustained charge or discharge rate of 2.5kW, I think peaking to 3kW.
Now for the two real deal-breakers....
A non-optional "maintenance" cycle where the cell must be completely discharged and the plates cleaned. While this is automatic and doesn't require manual intervention - it does mean that every (roughly) 100-120 hours of operation, you're going to be offline for somewhere between 40 mins and several hours. So you're going to want grid backup, or generator backup, or another cell (assuming 2.5kW is enough for your needs).
And the price of around $13,000 for the cell alone (around $19,000 with all its bits and bobs), no DIY - must be one of their approved people, and basically a 12-month guarantee.

They're also heavy (compared to lithium, but not so heavy as lead) at around 250Kg (550lbs) for  a 10kWh cell, and they need a ventilated area.

If you've got millions of dollars of investor money and you're building the fanciest site out of all the coolest bits you can find... sure. But for most of us they are just far too expensive and have far too many downsides.

[Westbranch]

Hi Ross, I had a few emails with them a few years ago and another point they made was that if you need more power than the unit can deliver in a set amount of time, think AGM dumping its power 'NOW!', you would probably need a separate bank of lead batteries that you slowly recharge from the RedFlow.... redundant duplication ... why 2 banks vs 1... ?

We should probably start another thread , so as to stay on topic,  Tom??

[TomW]

Hope this topic split off was accurate, I did not find the original Redflow post quoted by Ross.

Golly, only a couple more days til the days start getting longer! Can't make much Solar power in 9 short sun hours and 30% of that being shaded.

Seasonal type best wishes to everyone and hope you are healthy and happy.

Tom

[RossW]

Hi Ross, I had a few emails with them a few years ago and another point they made was that if you need more power than the unit can deliver in a set amount of time, think AGM dumping its power 'NOW!', you would probably need a separate bank of lead batteries that you slowly recharge from the RedFlow.... redundant duplication ... why 2 banks vs 1... ?

Well, if you're trying to get away from all the downsides of lead-acid, it seems utterly inconcievable to me that you'd then add another lot just to provide for all the shortcomings of the uber-expensive flow-cells!

Even the zcell doesn't have an infinite life - and if you amortize its cost over its expected life, it still doesn't stack up well against other "well known" technologies like lead-acid (flooded or agm) or LFP.

[Westbranch]

Exactly, my closing line there was meant to show my puzzlement of having a bank (AGM) that gives me what I want supported by a bank (RedFlow) that does NOT serve me well... and now I see it has very poor efficiency...  I guess it is best suited to the Oz outback... lots of sun, maybe too much for us... and above freezing temps most of the time 99.98% ...

LiFePo4 would be a lot better choice as it has FLA capabilities to serve large loads and not have to reach Float regularly  (or ever?).

[RossW]

LiFePo4 would be a lot better choice as it has FLA capabilities to serve large loads and not have to reach Float regularly  (or ever?).

Yes, this. 2 years ago I replaced my aging, second-hand AGM (2 x 500AH banks) with a 300AH LiFePO4 (LFP) bank.
Our dollar was very good then, and that only cost me $5K, however on every metric I have, this new bank outperforms my old 1000AH storage. It's stiffer, it soaks up current effortlessly, it has higher cycle efficiency, it handles transients better, its output voltage remains almost constant. On top of that I replaced over 1.6 tonnes of lead-acid batteries with a mere 370 lbs of LFP (so 90% lighter) and the new bank fits in less than 1/4 the space of the lead! The LFP cells have not demonstrated any memory effect, don't seem to get "lazy" when not fully charged and floated (or when they HAVE been!)...

I need additional capacity now because of some additional base load that I'm adding. It will be LFP, not zcells.

[grgdgreek]

What brand lfps are you using?

George

[RossW]

What brand lfps are you using?

They were made by a company in China called "High Power", but they seem to have disappeared. Their old website still exists, but no replies to email, their old phone numbers are disconnected or re-assigned...

Here's one:


And here's them all unpacked, but before they were installed.